Build of 14 on 13 creates a file which needs libdialog.so.9

Am experimenting with stable/14 to see how it goes, but have an odd problem. I
am compiling it on a stable/13 machine, as I was upgrading a 13 box to 14. But having
done this, I now cannot don an installworld again with a slihtly more recent compile,
as it fails, telling me that I need libdialog.so.9

The culprit appears to be /usr/src/amd64.amd64/tmp/legacy/bin/tzsetup which needs the
shared object. It exists on 13 so my first installworld succeeds, but after installing 14
it then fails as 14 does not have this library

Is what I am doing wrong? Is it true that once I have gone to 14, I can no longer install
again a version which was compiled under 13 ?

-pete.